Attorney General Jeff Sessions says he urged the firing of former FBI Director James Comey because of Comey’s handling of the Hillary Clinton email investigation.

Sessions says he gave President Donald Trump his opinion on Comey at Trump’s request. But, under questioning by Democratic Sen. Dianne Feinstein, Sessions refused to say whether he also discussed with Trump Comey’s involvement in the Russia investigation.

Sessions, speaking Wednesday before the Senate Judiciary Committee, said he won’t disclose his private conversations with Trump, citing longstanding Justice Department policy against the practice.

Sessions wouldn’t say when he first discussed Comey’s conduct with Trump. But Sessions said the errors of Comey’s handling of the Clinton email case can’t be overstated. He said Comey usurped prosecutors when he announced Clinton would not face criminal charges.